1. Field of the Invention
The invention relates to compositions useful for multifunctional printing, e.g., inkjet, dry and liquid toner electrophotographic (EP) printing, and recording sheets made with the composition.
2. Discussion of the Background
Commercially available, coated substrates for multifunctional printing, e.g., inkjet and liquid and dry toner electrophotographic (EP) printing currently do not provide sufficient toner adhesion for liquid toner digital printing presses. One example of a liquid toner digital press is the Indigo digital press available from Hewlett-Packard. The commercially available substrates are typically given a special surface treatment, which is applied prior to the printing process. Two special surface treatments are currently used: the so-called, “Sapphire” treatment, which is used for paper substrates; and the so-called, “Topaz” treatment, which is used for plastic films. In these treatments, a thin layer of polyethylene imine (PEI) is applied to the paper or plastic surface. WO 96/06384 describes the use of PEI or derivatives thereof or polyamides to impart a basic functionality to paper for use in liquid toner EP printing.
The Sapphire and Topaz treatments are costly because they require an off-line coating step after the paper has otherwise been completed. They are also unsatisfactory from a performance standpoint. Sapphire-coated papers perform only inconsistently due to aging of the chemical coating. The PEI-coated paper must be used within six months to ensure adequate toner adhesion. The PEI coating will also yellow over time. As such, these treatments are not a long term solution for EP printing.
US 2004/0244928 describes a paper composition suitable for liquid toner EP printing which avoids the use of PEI and which contains starch, an acrylic acid polymer, an organic material having an HLB value of about 2 to about 14, and water.
Other treatments have been advanced to enhance toner adhesion in liquid toner EP processes, but these are similarly unsatisfactory. EP 0879917 describes the use of an aluminate salt or a salt of a weak acid and a strong base to impart a basic functionality to the paper surface. It is disclosed that the use of a starch or other sizing agent is preferred. EP 116524 describes a paper substrate that contains an insoluble aluminum trihydrate in the base paper or magnesium sulfate, polyvinylpyrrolidone, starch, and polyvinyl alcohol at the paper surface. None of these treatments, however, provide adequate toner adhesion for the liquid toner used in digital EP printing, and none are suitable for multifunctional printing.
The inventors have discovered and solved the aforementioned problems and provide herein a composition and recording sheet that is suitable for liquid toner EP printing, dry toner EP printing, and inkjet printing.